Enhanced  imaging method and apparatus

ABSTRACT

This invention provides accurate, high quality images for the identification of the surface characteristics of an object, that may be used as an input to suitable industrial process. It involves acquiring a first raw scan of a portion of a target object across a scan line in a scan zone with a first camera and simultaneously acquiring a second raw scan of the same portion of the target object across the scan line in the scan zone with a second camera. The raw scans are converted to digital and then processed with flattening coefficients derived from measurements of variations in illumination. The first and second cameras sets of flattened image data are then gridized to compensate for parallax, make them orthographic sets of image data that can be compared on a pixel-by-pixel basis with a known or measured geometric profile of the target. A selection of enhanced pixel value for a surface coordinate can then be made, based on both sets of data. The obscuring of surface features by specular reflection can thus be effectively eliminated.

FIELD OF THE INVENTION

This invention relates generally to a method and apparatus for theidentification of the surface characteristics of an object, and moreparticularly to a non-contact system to generate image datarepresentative of surface reflectivity of an object that may be used asan input to suitable industrial process control apparatus.

BACKGROUND OF THE INVENTION

The invention will be described primarily in connection with using lightto obtain image data representing surface reflectivity of the externalsurfaces of boards of sawn timber in order to enable the computing ofaccurate image data of the three-dimensional surface profile of eachindividual board, for the purpose of adjusting sawing equipment in sawmills. This is important in a world of diminishing resources to optimizethe quantity or value of the lumber produced. Image data is assembledfrom a sequence of surface scans of a board as it moves past a linearsensor of scanning apparatus. A typical scan would record image data2048 pixels long by 1 pixel wide. However, area cameras could be usedand larger swaths of pixel data would accordingly be input for imageprocessing. Having computed the image of a board from scan data,algorithms can be applied that decide on the optimal placement of cutsby automated equipment in order to achieve desired characteristics ofboards with minimal waste pieces. The surface features of the boardcaptured in the image data disclose irregularities such as knots to beavoided or placed in order to meet the criteria for pieces to be madefrom the board. However, the invention is also applicable to measurementof other objects where rapid and accurate image capture may bebeneficial.

The state of the art in target object imaging for industrial processinghas been the obtaining of geometric, dimensional information from whicha computer model of the object is constructed as if the object werehomogeneous in composition.

The simplest non-contact automatic method commonly used to determine theshapes of boards is known in the prior art as shadow scanning. The boardmoves past a row of beams of light and the cross-sectional width of theboard is determined by measuring the shadow cast by the board on anarray of sensors on the other side of the board, which sensors are linedup with the projected light beams. Beams of light must be applied fromseveral directions and sensed by a corresponding set of sensor arrays toobtain even a rough profile. The shadow method cannot measure or evendetect concave features such as hole in the board. It measures the outerenvelope of the profile of the board.

Other methods known in the prior art for determining the shape of anobject without contact depend on the principle of triangulation, whichhas been known historically prior to the present century. Theapplication of this principle can be illustrated by considering a singlebeam of light transmitted in a known direction in space from a knownlocation at an object being measured. Some suitably selected form ofreceiving system positioned so as to view the object from a directiondifferent from the direction at which the light was transmitted detectsthe direction from the receiving system at which the reflection from theprojected light spot appears on the object being measured. The distancebetween the transmitter and the receiver is known and fixed. Hence twoangles (determined from the transmitting and receiving directions) andone side of a triangle (the distance between the transmitter and thereceiver) are determined, and thus the location of the spot on theobject relative to the measuring apparatus is easily calculated.Triangulation is generally used to obtain geometric views and cannot byitself provide images of surface appearance variations that are notcorrelated with changes in geometric shape of the target object.

The present invention now provides a method and means for capturingenhanced surface appearance data and adding it to the geometric image ofa target object.

Many industrial scanning applications require fast image capture(digital pictures) of target surfaces. All physical targets reflectincident light that falls on a surface in one of two kinds ofreflection: specular reflection or diffuse reflection. Geometricimaging, the measuring and calculating from a distance of the profile oftarget objects having irregularities of shape moving rapidly along aproduction line, is plagued by instances of specular reflection of thelight from the illumination source by various areas on the object to beimaged. Areas of specular reflection from the target object appear asoverly bright areas on camera images and also obliterate image accuracyregarding surface appearance characteristics quite apart from variationin surface shape.

Specular reflection-is the mirror-like reflection of light (or sometimesother kinds of wave) from a surface, in which light from a singleincoming direction (a ray) is reflected into a single outgoingdirection. Specular reflection results from the tendency for incidentlight to be reflected at the same angle as the incidence angle on theopposite side of a normal to the surface. A mirror is an example of avery good specular reflector. Diffuse reflection is the tendency forincident light to be reflected in an omni-directional manner above thetarget surface. An example of specular vs. diffuse reflection can befound in comparison of “glossy” vs. “flat” paints—glossy painted surfaceis much more specularly reflective when compared with a surface paintedwith flat paint.

High speed image capture systems, used to scan dynamic scenes, benefitfrom a high intensity illumination source because camera exposure andintegration time can then be reduced, enabling less smearing of thecaptured image and faster scan rates. This is particularly significantin industrial machine vision applications, when 2-dimensional images areobtained by combining a plurality of sequentially acquired linear scans.Machine vision is not restricted to 2 dimensional images generated froma plurality of sequentially acquired linear scans.

High quality image capture is desired or required in various machinevision applications to allow image processing to identify, isolate andclassify features of interest in the image. Some aspects of imagequality are predictable intensity response, ability to merge imagescaptured from adjacent but similar image capture systems, with minimum“stitching” features which may negatively affect image processing. Agood quality image having such characteristics can be obtained in animage acquisition system when only diffuse reflection—as opposed tospecular reflection—from the target object is included in the image.

A classic challenge with image capture systems is the illuminationsystem. Generally it is undesirable to have point-source lighting anddesirable to have “flat” or “soft” lighting, that is, diffuse lighting.Non-diffuse lighting can result in peculiarities of contrast and shadowon images of the target object due to the light source's position. Asource of light can be considered effectively a point source if theresolution of the imaging instrument is too low to resolve its size, orif the object is at a very great distance. To avoid hot spots created byspecular reflection of one or of a few point source illuminators, manyimage capture illumination systems employ a large plurality of lightsources and/or diffusing elements to try to minimize hot spots createdby the specular reflectivity.

With a high speed moving target, the illuminator should be a flashrather than sustained ambient light, in order to capture the requiredimage data for the system.

Historically, visual features of a board are only considered aftercutting, at a sorting stage. The present invention enables the moving ofsuch decisions upstream in the lumber milling process, and enables moreusable and higher value end product than the prior technology.

SUMMARY OF THE INVENTION

The present invention provides for accurate, high quality images of theobjects scanned by processing raw image linear scans (“Raw Scans”),which can be assembled sequentially to form raw images (“Raw Images”).The Raw Scans are acquired from separate cameras simultaneously. Thecameras may be CCD, CMOS linear sensors, or use other photo-sensitivedevices that responds to varying levels of light emanating from itsfield of view. Processing the Raw Scans as summarized below to addressdistortions, and combining the resulting processed images is done inorder to arrive at the desired high quality Enhanced Image, void ofspecular reflections, with uniformity of image where the object scannedhas uniformity of surface, and accurate portrayal of aberrant areaswhere the object scanned has such aberrations.

Two (or more) corresponding Raw Images (or two or more Raw Scans beforetheir assembly into Raw Images) from separate cameras are processed with“Flattening” and “Gridizing”. The resulting two (or more) correspondingFlattened and Gridized Images are then compared and portions of each areselectively combined to render an enhanced, accurate image (the“Enhanced Image”) of the target object. The “Selective Combining” usesthe segments of the processed Raw Scans that have only diffusereflection, and discards the segments of the scans that have specularreflection. Areas of specular reflection are thus essentially eliminatedin the Enhanced Images.

The accurate imaging method and apparatus presently disclosed willovercome distortions not only due to specular reflection (in theSelective Combining) but also due to variations deriving from theradiation pattern of the illumination source and responsiveness of thecameras along the pixel axis (by Flattening) and due to parallax (byGridizing). The elimination of the latter variations via Flattening andGridizing is necessary in order to use the Selective Combining methoddisclosed in more detail below. Flattening and Gridizing are thereforeperformed before the Selective Combining of the image data.

In Flattening, the Raw Scan data is compensated for illuminationradiation and geometric pattern variance, and particular sensitivitiesof each camera in use. Unrealistic image results, apart from the effectsof specular reflection, are mainly due to radiation geometric patternvariance from the illumination source to the scanned object, and toirregularities in camera sensitivity. In the present invention, bothillumination source and camera are fixed in position, so it is possibleto compensate for these image-distorting factors by calibrating out theeffects of these variations and get a flat video response. Beforeapplying the enhanced imaging method summarized above, a flatteningcalibration is done to obtain pixel amplitude correction coefficientswhich are a function of X (axis from target surface to scan head) and Y(axis across target object) coordinate locations in the scan zone. Asuccession of images of a stock, uniform “gray card”, available fromphotographic supply companies, are taken with each camera andcorresponding illuminator that is used in the system. A “gray card” ismanufactured with specified optical qualities, such as 18% reflectivityon one side and 90% reflectivity on the other side. The higherreflective side (e.g. 90% reflectivity) is used in order to get astronger video signal when doing the flattening calibration. A number ofscans are taken across Y at each X coordinate, in order to average outsystem video noise. The flattening calibration is repeated at a range ofX=X 1, then X=X 2 and so on, in order to get a base “flattened” videosignal level for each X and Y coordinate.

It is adequate for purposes of enhanced image board scanning to takesuch calibration scans at each ¼ inch along the X axis. For even greateraccuracy, finer increments of flattening calibration could be performed.Either way, computer calculations then provide interpolated values forfiner coordinates along X.

The flattening calibration scans are taken with each camera andcorresponding illuminator that is used in the system. The “gray cards”can be joined to form a strip long enough to cover the scan zone, andthe joining gap or overlap lines can either be attributed with adjacenttest values, or the strip can be moved after a first set of tests toplace non-joint areas in the former joint areas, and obtain “flattened”video for those coordinates as well. In practice it is often sufficientif the test scans are taken ¼″ apart. In Flattening the coefficients ofvariation for the test “flattened” video at all the coordinates acrossthe scan zone will be applied to the same coordinates of Raw Scan dataobtained from the actual target. After Flattening is applied to the RawScans, the results will be called “Flattened Scans.” The Flattened Scansmay be assembled sequentially into “Flattened Images”.

Regarding the Gridizing step, the problem with combining segments ofdifferent Raw Images of the same object taken from different cameras isthat the different Raw Images will have differing parallax. Parallax isthe perspective effect of angle and distance of different areas of thetarget with respect to the camera, an apparent displacement ordifference of orientation of an object viewed along two different linesof sight, and is measured by the angle or semi-angle of inclinationbetween those two lines. When two cameras at different locations areperforming Raw Scans to be combined later on a pixel by pixel basis toform a single accurate image of the target object, the parallax must becalculated and compensated. When a target object is at a known range,whether a board or a test sheet of paper on a plate of glass with aknown distance to a camera, the effect of parallax can be calculated andcompensated, in order to generate an orthographic image. “Gridizing” isperformed to compensate for the variation in the distance from thetarget to the imaging system. Undoing image parallax results in anorthographic image (the “Ortho Image”, or “Ortho” scan if dealing with asingle scan), as if the image was acquired at an infinite distance.

Parallax can be undone using either a calculated or calibrated methodand avoids using a special type of parallax-corrective lens known as atelecentric lens. A telecentric lens is a compound lens with an unusualgeometric property in how it forms images. The defining property of atelecentric system is the location of the entrance pupil or exit pupilat infinity. This means that the chief rays (oblique rays which passthrough the center of the aperture stop) are parallel to the opticalaxis in front of or behind the system, respectively. Such lenses arelarge, expensive, and typically have a small field of view, whichrenders them unsuitable for scanning long boards for example.

In order to calculate or calibrate to remove parallax from an image,prior knowledge of the physical distance of the target to the imagingsystem is required. When a target is at a fixed distance from a camerain a system, such as on a flat bed scanner, parallax compensation can becalculated/calibrated once for the camera and applied to every imagetaken with it thereafter. When a target may be present at differentdistances from the imaging system, or portions of the target are atvarying distances from the imaging system, each such distance at thetime of each Raw Image must be known to perform Gridizing.

Generation of the Enhanced Images thus comprises parallel stages foreach of at least a first and a second camera's respective capturedimages. The illuminator that was previously calibrated with the camerasfor purposes of Flattening shines on the target to obtain a scan foreach of Camera 0 and Camera 1. The method then proceeds with:

Camera 0 Raw Scan - - - Camera 0 Raw Scan Flattening - - - Camera 0Flattened Scan Gridizing

paralleled by

Camera 1 Raw Scan - - - Camera 1 Raw Scan Flattening - - - Camera 1Flattened Scan Gridizing

and then the respective (two, or more if more cameras are used)resulting Ortho Scans from each Raw Scan—Flattening—Gridizing parallelstage above are combined in a separate fourth step of SelectiveCombining:

Camera 0 Gridized (Ortho) Scan - - - combined with—Camera 1 Gridized(Ortho) scan

to result in an Enhanced Scan. The Selective Combining of best pixelamplitude from corresponding pixels in the respective Ortho Scansproduced Enhanced Scans. The Enhanced Scans can be assembled in order torender Enhanced Images.

It will be appreciated that the Method summarized above can be appliedto Raw Images that have been assembled from individual Raw Scans, theRaw Images from the respective cameras being then Flattened intoFlattened Images, the Flattened Images being then Gridized into GridizedImages (Ortho Images), and the respective Ortho Images then beingselectively combined into Enhanced Images. The place in the method atwhich scans are assembled into larger images is optional. It is simplerto apply the whole process to individual scans before their assemblyinto images, but it is not necessary to the invention, and with theappropriate calculations the assembly of scans into images could be doneat any stage or step of the method herein disclosed, and the remainingstages or steps then applied to the resulting images rather than to thescans.

The system of the present invention gives better results and worksfaster than using one physical camera while processing images taken withmultiple non-simultaneous illuminators shining at different angles onthe subject material. It is faster because the presently disclosedsystem does not have to wait to acquire multiple images from eachilluminator. A single image capture cycle is required and a higherproduction rate can be achieved.

The present invention works for moving targets—as both camera images arecaptured simultaneously, both acquired images are seeing the sameportion and hence features of the target object. If multiplenon-simultaneous illuminations are used in a moving target system, forexample, when the target is on an assembly line or conveyor belt, thetarget will have moved between illuminations, resulting in the loss ofcorrespondence between features imaged on each of the non-simultaneousacquired images.

A distinction must be made between a) designed “scanning” movement ofthe target or of the scanner, along a (typically horizontal) plane (suchas a conveyor belt), with an intended constant distance between ascanner camera sensor mount head and a surface of interest on thetarget, and b) unintended “target range” movement in the distancebetween scanner head and target, such as may occur due to vibration ofequipment or to varied 3-dimensional topographical features of thetarget. The “moving targets” above refers to the designed “scanning”movement.

In the accurate imaging system of the present invention, scanningmovement is tightly controlled, with microseconds tracked. The level oftemporal latency is designed to enable accuracy on the order of 1/1000thinch for spatial control of the target position during a scan. It isimportant that both corresponding Raw Images from the parallel stagesnoted above be combined properly to capture the same portion of thetarget for the eventual Enhanced Image. It is theoretically possible touse area cameras to acquire multiple images from multiple illuminationsources of a moving target object, for later input into calculationsabout the object, but it would be far more computationally intensivethan the method herein disclosed. When too many pixels form the imagedata, any inadvertent target movement (as opposed to intended,controlled target movement for successive scans) vastly increases theproblem of compensatory calculations. This is of even greater concern inthe case of more than two cameras being used simultaneously in thisaccurate imaging process.

To acquire the Raw Images, and maintain a known image aspect ratio—aPosition Encoder is used to track the position of the target as itmoves. Position encoders are used to generate an electronic signal thatindicates an absolute mechanical position, or an incremental mechanicalmovement relative to a reference position. Preferably the encoder isused to trigger scan captures at correct physical intervals or lessdesirably to select the desired image from an oversampled set of scans,said selection criteria to determine the acquired image aspect ratio.

For elimination of specular reflection, the physical arrangement ofprojector and two cameras should be such that the cameras havesufficient physical separation to avoid both cameras receiving the samereflected light and imaging a highly specular reflective portion of thetarget. In the photographic terms of “far field” and “near field”, theplacement of the cameras in relation to the scan zone is such that thetarget is essentially in the cameras' “far field”. It is a physical factthat regardless of the surface characteristics of the target, camerasseparated from each other and from an illuminator along an axis parallelto a raw scan line on the target object cannot both receive an overlybright, specularly reflected patch of light from the same patch of thetarget object illuminated by a point-source (or effectivelypoint-source) illuminator. For each camera there is one and only onespecularly reflective beam path (at which the angle of reflection equalsthe angle of incidence) between the illuminator and the camera, and eachof those beam paths strikes the target object at different areas.

Following Flattening and Gridization of the corresponding Raw Scans fromthe multiple cameras, the resulting Ortho Images are comparable on ageometric response level, as they have acquired images from the sametarget, and both (all, in the case of more than two cameras) of thecorresponding Ortho Images represent a view from a distance of infinity.In other words, a given feature from the target appears in both imagesat the same location. The images are therefore now comparable on a pixelby pixel basis. Higher video signal amplitude pixels as between Camera 0Ortho (scans or images) and Camera 1 Ortho are the result of specularreflection as opposed to diffuse reflection. This is key to enableselection of portions of each Ortho Image for inclusion in one EnhancedImage, in order to generate an accurate image of the target withoutareas of specular reflection distorting the image. After the Flatteningand Gridizing are performed on the Raw Scans, the resulting Ortho Imagesof the target from each camera will have a pixel to pixel comparisonpossible with respect to amplitude response for each defined geometriclocation on the target object. The Selective Combining can then beperformed. Corresponding pixel amplitudes representing respectivesegments of the target object in each of the two or more correspondingOrtho Images are compared, and the lower value is selected for inclusionin the Enhanced Image. In the Gridizing step, it is also possible toachieve improved imaging by selecting an average of the correspondingpixel amplitudes or by taking part of one pixel and part of another,particularly if both are within a known normal range for the targetbeing imaged. Excellent results can also be obtained by applying thethree steps of the parallel stage and then the Selective Combining onevery other pixel in a pair of 2048-pixel-long×1 pixel wide Raw Scans,combining the other pixels of data—this effectively uses 1024 pixels ofdata per scan and cuts in half the data computed, yet provides moreaccurate enhanced images than using 1024-pixel or even 2048-pixel datawithout the method of the present invention.

The enhanced imaging method and apparatus of the present inventiongenerates multiple images of a target object and makes them comparableon a pixel-by-pixel basis. The comparing requires either a knowndistance to a flat surface, a known set of distances to a complexlyengineered surface (such as a curved windshield, which could beinspected by the method and apparatus for surface features such ascracks). or a geometric scan of a varying surface to obtain itsgeometric profile.

The state of the art in geometric scanning uses coded light from a laserto obtain a geometric scan of the target object at each X and Ycoordinate within the scan zone. It is also possible to use a “sheet oflight” method from the prior technology to obtain a geometric profile ofthe target object, but that method would involve having an area cameraupstream or downstream of the imaging scan head. All these and relatedmethods and apparatus to obtain the geometric profile of a target objectare herein referred to as “structured light geometric scanning” Theimage capture method and apparatus presented here allows high intensitypoint source or near point source lighting, yet eliminates or greatlyreduces the occurrence of specular reflectivity in the final enhancedimage for the image capturing system. A single LED or a laser is anexample of what is meant by “point source” in this disclosure. An arrayof LEDs is an example of a near point source for purposes of thisinvention. Indeed, in the present invention, a point source or nearpoint source is desirable because:

-   -   a) it can be integrated efficiently into a scan head housing;        and    -   b) it allows the cameras and the illuminator to be placed all in        a co-planar arrangement in the scan head, which renders the        calculations of the invention method to be simpler than if those        elements were not aligned.

One preferred arrangement for the illumination elements in the apparatusof the present invention is to use a coded light laser for obtaining ageometric profile of the target object, and an LED array comprising 15LEDs in a row, aligned with but between the first and second cameras,for obtaining the raw data that will be processed into the enhancedimage data by the method summarized above. The geometric profile data isused to identify coordinates on the target object surface that will bemapped to the Raw image data acquired by each of the separated camerasand thus to the corresponding Flattened and Gridized image data in theparallel paths from Raw to Gridized (Ortho) Images, and thence to theEnhanced Image. It is possible to use the invention without using acoded laser or other geometric profile detection means if the geometricprofile of the target object is already known and computed. For example,the invention could be used to detect surface anomalies such as cracksin a precision-manufactured article such as a glass windshield. There isalso an important distinction between using “structured r light (such asa coded laser) to scan and compute the shape and position (geometricprofile) of a surface and using an uncoded laser as one kind of targetilluminator for the first and second cameras while obtaining the firstand second raw data. An uncoded laser can be used to obtain monochromeraw image data by each of the first and second cameras, whereas LEDsprovide suitable illumination for obtaining color raw image data. Inorder to obtain and use both monochrome and color raw data, therespective illuminators must be cycled, for example, flashedalternately.

The invention can work with area lighting, or with continuousillumination from a point source or near point source, but the need forrapid multiple scans in an industrial process demands high intensityillumination to enable fast scan and exposure times by the cameras. LEDsfor example can operate at a much higher intensity if they are flashedon and off as needed by the cameras, with the off times allowing forheat dissipation. Heat is a limiting factor in both the life andperformance of LEDs. Turning off an illuminator between the scans thatneed the particular illuminator also conserves electrical power. In anyevent, the alternating illumination is necessary to allow multiplexingbetween the geometric profiling of the target object with structuredlight, and surface appearance raw data acquisition by the first andsecond cameras. It is also useful to the acquisition and integration ofboth monochrome and color raw data by the method and apparatus of theinvention. A computer control is used to trigger the illuminators at thedesired times.

The invention provides a method for generating accurate, high qualityimages comprising the steps of:

-   -   a) acquiring a first raw scan of a portion of a target object        across a scan line in a scan zone with a first camera and        simultaneously acquiring a second raw scan of the same portion        of the target object across the scan line in the scan zone with        a second camera, the second camera being separated from the        first camera in a camera zone such that the first and second        camera have substantially different perspectives of the same        portion of the target object;    -   b) converting the first raw scan from analog to digital format        resulting in first raw image data and converting the second raw        scan from analog to digital format resulting in second raw image        data;    -   c) processing the first raw image data with a first set of        flattening coefficients derived from measurements of variations        in illumination and in first camera response across the scan        line to a uniform diffusely reflecting target in the scan zone,        resulting in first flattened image data from the target object,        and processing the second raw image data with a second set of        flattening coefficients derived from measurements of variations        in illumination and in second camera response across the scan        line to the uniform diffusely reflecting target in the scan        zone, resulting in second flattened image data from the target        object;    -   d) compensating for parallax in first flattened image data with        a first set of calculations, resulting in first orthographic        image data,; and compensating for parallax in second flattened        image data with a second set of calculations, resulting in        second orthographic image data;    -   e) comparing first orthographic image data corresponding to a        coordinate location on the target object with second        orthographic image data corresponding to the coordinate location        on the target object;    -   f) selecting a pixel intensity value, for use as enhanced image        data representing the coordinate location on the target object,        from:        -   i) the first orthographic image data corresponding to the            coordinate location;        -   ii) the second orthographic image data corresponding to the            coordinate location;        -   iii) a result of a formula using a combination of the first            and second orthographic data corresponding to the coordinate            location.

Regarding step d) above, the parallax inherent in the first flattenedimage data is different from the parallax inherent in the secondflattened image data, and both must be compensated with the respectivesets of calculations in order to arrive at first and second orthographicimage data. It is those different orthographic sets of data which canthen both be compared on a pixel by pixel basis and identified with asingle geometric point on the actual target surface.

Regarding step f) above, one example would be to choose a pixelintensity value from the first orthographic image data over thecorresponding data from the second orthographic data (both correspondingto the coordinate location of that pixel in the geometric data), becausethe pixel intensity value for that location was lower in the firstorthographic data than in the second orthographic data. Another example,falling under f) iii) above, would be to take a weighted averageintensity value for that pixel, drawn from both the first and secondorthographic data. The use of such a formula could depend on theparticular target object surface characteristics and the desired type ofEnhanced Image to be obtained from it. In practice, the steps of Claim 1are repeated with scanning of sequential scan lines across the targetobject, resulting in sequences of enhanced image data representingcorresponding coordinate locations on the target object, and assemblingan enhanced image of the target object from the sequences of enhancedimage data. The movement of the target object during scanning iscontrolled to maintain a known image aspect ratio during scanning and toavoid distortion of the enhanced image. An electronic signal from aposition encoder is used during the scanning to indicate target objectposition relative to a reference position for the scan zone. Forexample, the target can ride a conveyor belt along a z-axis below thescan head. Alternatively, there may be an industrial situation in whichit is preferable to move the scan head along the z-axis over the targetobject, for example, where the target is very heavy. The positionencoder need not be aligned with the z-axis. It could sense andcalculate z-axis motion although its sensor to target path was forexample at 45 degrees to the z-axis. In any event, scans are triggeredby the position encoder at known incremental intervals of a targetobject movement through the scan zone.

To counter specular reflection, the pixel intensity value selected foruse as enhanced image data would be the lower of two correspondingorthographic pixel data values from first orthographic data and fromsecond orthographic data, thereby selecting lower specular reflectionfrom the target object.

The geometric positions of relevant portions of the target object can beobtained by structured light geometric scanning, enabling mapping offirst raw data pixels to corresponding second raw data pixels. If acoded laser is used for the structured light (rather than using bands ofcolored light, for example), it should be noted that this use of a laseris different from the use of uncoded laser light in a variant of thesystem in which an uncoded laser illuminator is used in conjunction witha monochrome camera to obtain at least one set of raw image data inmonochrome. In many situations, however, the most informative raw imagedata would be obtained by using an LED to illuminate the target objectfor the first and second cameras during an image capture scan.

Alternate firing, from a structured light geometric scanner illuminatorto obtain target object surface profile and from a raw image datailluminator to obtain raw data for image, is made effectivelysimultaneous with respect to z-axis scanning movement of the targetobject by having a time between flashes from the respective illuminatorssufficiently short that a computed adjustment of coordinate positions tocompensate for scanning movement of the target object between firings iswithin computational limits for correlating resulting structured lightgeometric profile data and corresponding raw image data to pixelresolution.

It is convenient to apply the Enhanced Imaging method and apparatus toindividual successive scan lines of raw data, ending up with a “scan”line of Enhanced data, with sequential Enhanced lines being thenavailable for assembly into a large two dimensional image. However, theassembly of successive “scan lines” could be done at any stage afterobtaining the raw data, with the remaining steps then applied to the twodimensional image data.

In an industrial application with wide target objects, both:

-   -   a) the processing of the first raw image data with a first set        of flattening coefficients derived from measurements of        variations in illumination and in first camera response across        the scan line to a uniform diffusely reflecting target in the        scan zone, resulting in first flattened image data from the        target object, and    -   b) the processing of the second raw image data with a second set        of flattening coefficients derived from measurements of        variations in illumination and in second camera response across        the scan line to the uniform diffusely reflecting target in the        scan zone, resulting in second flattened image data from the        target object,        would be performed to a standard level of image flattening with        multiple identical adjacent scan heads each using an        illuminator, a first camera and a second camera, and the        processing method of the invention. Multiple flattened images of        adjacent areas on the target below adjacent scan heads obtained        by such processing can then be joined to form an overall image        of the target without significant discontinuity of image        accuracy between multiple enhanced images from respective        adjacent scan heads. The invention enables a geometrically exact        stitch line between such joined images and obviates grotesque        overlapping of portions of adjacent Enhanced Images. The pixels        on the stitch line itself can be selectively combined from        adjacent sets of Enhanced Image data. In a preferred embodiment,        multiple images of adjacent areas on the target object would be        joined together by truncating and aligning along a stitch line        that is exact to each pixel (rather than overlapping adjacent        images), in order to minimize discontinuity of target object        features, and to minimize discontinuity of image intensity        values for adjacent geometric locations on the target object to        below image background noise values.

The method disclosed above can be preformed with the apparatus indicatedherein. Each step of processing of the relevant data can be performed bya central computer or by a dedicated processing module. The apparatusshould include:

-   -   a) at least two cameras, including a first camera set up for        acquiring a first raw scan of a portion of a target object        across a scan line in a scan zone with a first camera and        simultaneously acquiring a second raw scan of the same portion        of the target object across the scan line in the scan zone with        a second camera, the second camera being separated from the        first camera in a camera zone such that the first and second        camera have substantially different perspectives of the same        portion of the target object;    -   b) an analog to digital converter set up for converting the        first raw scan from analog to digital format resulting in first        raw image data and converting the second raw scan from analog to        digital format resulting in second raw image data;    -   c) a flattening image processing module that processes the first        raw image data with a first set of flattening coefficients        derived from measurements of variations in illumination and in        first camera response across the scan line to a uniform        diffusely reflecting target in the scan zone, resulting in first        flattened image data from the target object, and that processes        the second raw image data with a second set of flattening        coefficients derived from measurements of variations in        illumination and in second camera response across the scan line        to the uniform diffusely reflecting target in the scan zone,        resulting in second flattened image data from the target object;    -   d) a gridizing image processing module that compensates for        parallax in first flattened image data with a first set of        calculations, resulting in first orthographic image data, and        compensates for parallax in second flattened image data with a        second set of calculations, resulting in second orthographic        image data;    -   e) a selective combining image processing module that compares        first orthographic image data corresponding to a coordinate        location on the target object with second orthographic image        data corresponding to the coordinate location on the target        object and selects a pixel intensity value, for use as enhanced        image data representing the coordinate location on the target        object, from:        -   i) the first orthographic image data corresponding to the            coordinate location;        -   ii) the second orthographic image data corresponding to the            coordinate location;        -   iii) a result of a formula using a combination of the first            and second orthographic data corresponding to the coordinate            location.

As an example under e) iii) immediately above, the selective combiningimage processing module could appropriately be programmed to take anaverage value of intensity for any give pixel location from the firstand second orthographic data, if that pixel fell on an edge of theEnhanced Image to be used in abutment with an Enhance Image from anadjacent apparatus of an extended target object, such as a log, or longboard.

Preferably, the apparatus further comprises a computer set up to obtainsequential scan lines across the target object and sequences of enhancedimage data representing corresponding coordinate locations on the targetobject, and to assemble an enhanced image of the target object from thesequences of enhanced image data, and a position encoder set up to trackmovement of the target object during scanning in order to maintain aknown image aspect ratio during scanning and to avoid distortion of theenhanced image. The computer can also be set up to perform imagestitching from adjacent scan heads, each of which has an instance offirst and second cameras, and imaging illuminator. Preferably, each scanhead would also have a coded light, laser illuminator for providinggeometric profile data from the target object to the computer.

The selective combining image processing and other modules can beembodied in hardware or a combination of software and computer hardware,programmed to select for use as enhanced image data a lower of twocorresponding orthographic pixel data values from first orthographicdata and from second orthographic data, thereby selecting lower specularreflection from the target object.

A structured light geometric scanner, which is known technology, can beused to obtain for obtaining geometric positions of relevant portions ofthe target object. It is new however to use this information for themapping of first raw data pixels to corresponding second raw data pixelspreparatory to the Flattening, Gridizing process modules. Likewise, itis commonplace to use LED illuminator in conjunction with a color camerato obtain color images, but it is new to use them with a second camerain the manner described by which different by corresponding sets of rawimage data are sent first through a Flattening module and then through aGridizing module, and finally through a Selective Combining module, toarrive at an Enhanced Image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the basic steps and elements inthe enhanced imaging method and apparatus of the present invention.

FIG. 2 is a schematic diagram showing an example of the apparatus' scanhead coordinate system geometry and scan zone.

FIG. 3 is an optical schematic diagram showing some of the light pathsin a two-camera, two illuminator example of the apparatus.

FIG. 4 is a perspective drawing illustrating Specular Reflection versusDiffuse Reflection.

FIG. 5A is a graph of Projector Radiation pattern.

FIG. 5B is a graph of three Projector Radiation patterns, at threedistances along the X-axis from FIG. 2.

FIG. 6A is a graph of GrayCard Raw Image data from Camera 0, withaberration “dips” that reflect obvious lines on the GrayCard.

FIG. 6B is a graph of the corresponding GrayCard Raw Image data fromCamera 1, showing different aberration “dips” from FIG. 6A.

FIG. 7A is a graph showing the calculated Flattening Coefficients forCamera 0.

FIG. 7B is a graph showing the calculated Flattening Coefficients forCamera 1.

FIG. 8 is a block diagram showing the obtaining of FlatteningCoefficients for later use in the Flattening subprocess.

FIG. 9 shows the beginning and end of a long Spreadsheet of GrayCardimage data.

FIG. 10A is a graph of Flattened Image data from Camera 0.

FIG. 10B is a graph of Flattened Image data from Camera 1.

FIG. 11 shows the problem of parallax in using two separated cameras toview the same area of a target surface.

FIG. 12A is a graph of Ortho Image data (i.e. Flattened and Gridized)from Camera 0, from a target GrayCard.

FIG. 12B is graph of Ortho Image data (i.e. Flattened and Gridized) fromCamera 1, from a target GrayCard.

FIG. 13 is a front view of a scan head containing Camera 0, Camera 1,and an illuminator, a length of lumber, and bars of coded light.

FIG. 14A is a graph of Raw Image data from a striped target, from Camera0, showing an middle aberration on the striped target.

FIG. 14B is a graph of Raw Image data from the striped target, fromCamera 1, showing a different placement of the middle aberration on thestriped target from FIG. 14A.

FIG. 15A is a graph of Ortho Image data from the striped target, fromCamera 0, after Gridizing.

FIG. 15B is a graph of Ortho Image data from the striped target, fromCamera 1, after Gridizing, showing the middle aberration from thestriped target is now aligned along the horizontal axis the same as inFIG. 15A.

FIG. 16A is an actual image from Raw Image data from Camera 0, showingan area of specular reflection in the middle area of target objectboard, and an indication of other aberrations in the board to the right.

FIG. 16B is an actual image from Raw Image data from Camera 1, showingan different area of specular reflection, nearer to the right side ofthe same target object board, and an indication of an aberration in thecenter of the board corresponding to the area specular reflection inFIG. 16A.

FIG. 17A is an actual image from Ortho (Flattened and Gridized) Imagedata from Camera 0.

FIG. 17B is an actual image from Ortho (Flattened and Gridized) Imagedata from Camera

FIG. 18 is a block diagram showing the Selective Combining from OrthoImaga data from Camera 0 and from Ortho Image data from Camera 1, toresult in an Enhanced Image.

FIG. 19A is a graph of three lines of Image output data, one from OrthoImage 0, one from Ortho Image 1, and a line of Enhanced Image datagenerated by selectively combining data from Ortho Image 0 and OrthoImage 1.

FIG. 19B is an actual Enhanced Image formed from Raw Image data with themethod and apparatus of the present invention.

FIG. 20 is a schematic representation of a series of four scan heads,scanning four respective overlapping segments of a long board.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an illuminator 16 shines light 107 on a targetobject 17. A mixture of diffuse and specular reflection occurs alongvarious beam paths such as at 108 and 109 to Camera 0 and to Camera 1respectively. Light input to Camera 0 is put through A/D Conversion 2 inan analog/digital converter, which outputs a set of Raw Scan 0 data 4.The Raw Scan 0 data 4 then proceeds through the Flattening 6 process,which corrects each pixel for variance in illumination pattern andcamera sensitivity. The Flattened Scan 0 data 8 then proceeds to aGridizing 10 process, which corrects the data for parallax effect, thatis, for the widening of pixel spaces at more oblique angles across thetarget surface from Camera O′s perspective. The resulting OrthographicScan 0 data 12 then proceeds to the Selective Combining module 14.

Likewise, light input to Camera 1 is put through A/D Conversion 3 in ananalog/digital converter, which outputs a set of Raw Scan 1 data 5. TheRaw Scan 1 data 5 then proceeds through a Flattening 7 processcorresponding to Flattening 6 for the other Camera(0)'s output path. TheFlattened Scan 1 data 9 then proceeds to a Gridizing 11 processcorresponding the Gridizing 10 above for the other Camera (0)'s datapath. The resulting Orthographic Scan 1 data 13 then also proceeds tothe Selective Combining module 14.

The Selective Combining module 14 uses a pre-selected method ofcomparing Ortho Scan 0 data with Ortho Scan 1 data, on a pixel by pixel,or group of pixel by corresponding group of pixel basis, and the datathat best matches Selective Combining criteria, such as lower image datavalue for each corresponding pixel from Ortho Scan 0 and Ortho Scan 1,is used, on the assumption that higher data value indicates specularrather than diffuse reflection.

A Computer Control 19 uses a Position Encoder 18, a known device inindustrial assembly lines, to track the position of the target object 17in the scan zone and to map readings from Camera 0 and Camera 1 toparticular locations on the target object as the scanning proceeds. TheComputer Control also times and fires the Illuminator 16, applies theFlattening coefficients to Raw Scans 0 and 1 in the Flattening 6 and 7processes, calculates and applies corrections for parallax in Gridizing10 and 11, and enables user control over the Selective Combining 14criteria to be applied to result in the Enhanced Image 15.

Referring to FIG. 2, a scan head 21 houses the cameras and illuminatorsthat are used to acquire the sets of Raw Image Data. The scan head 21 ispositioned directly over a scan zone 22 through which the target objectcan be conveyed. (Alternately, of course, the scan head 21 could betracked over the scan zone 22 in which a stationary target object isscanned.) The vertical X-axis 23 runs from the center of the scan head21 through the center of the scan zone. The scan zone 22 has a depth offield 28 (e.g. 8 inches) within which the target object 1will be insuitable focus for the cameras of the scan head. The horizontal Y-axis26 traverses the width of the scan zone 22. A typical width for the scanzone would be 2 feet and a typical distance 25 between scan head 21 andscan zone would be 2 to 3 feet, but other distance arrangements withsuitable cameras and illuminators would of course work. Likewise, auseful scan head height 29 is approximately 6 inches for lumber millapplications, sized such that cameras, lens, illuminators, scan windows,and related circuit boards are all contained within a sturdy housing.

Referring to FIG. 3, Camera 0 (item 33) has a field of view 35 thatcovers the entire scan zone 22, from line 35 a to the target object scanzone upper left point 39, to line 35 b to the target object scan zoneupper right point 40. Likewise, Camera 1 (item 34) has a field of view36 that covers the entire scan zone 22, from line 36 b to the targetobject scan zone upper right point 40, to line 36 a to the target objectscan zone upper left point 39. A laser illuminator 31 provides codedlight over the entire scan zone 22, with a coded laser field ofprojection 37, from line 37 a to the target object scan zone upper leftpoint 39, to line 37 b to the target object scan zone upper right point40. An LED illuminator 32 provides broad spectrum light over the entirescan zone 22, with an LED field of projection 38, from line 38 b to thetarget object scan zone upper right point 40, to line 38 a to the targetobject scan zone upper right point 39.

FIG. 4A illustrates specular reflection, in which incident light 42 isreflected from object 41, with essentially all of the resultingreflected light 43 leaving the object at the same angle 44. A camerareceiving the reflected light 43 would “see” a patch of glare on theobject 41 rather than detailed image information for the object in thearea of reflection. FIG. 4B illustrates diffuse reflection, in whichincident light 42 is scattered from object 45, resulting in variousreflected beams of light such as at 46, 47, 48 and 49. This type ofreflection, when viewed by an imaging system, can provide image detailfor the object 45. The nature of specular reflection is that from asingle illuminator source, the specular reflection off a portion oftarget can only be captured (undesirably) by one of two cameras that arephysically separated along a line above the target on which theillumination source is also aligned.

If a point source (or near-point-source) illuminator (such as LEDilluminator 32 in FIG. 3) projects light across the scan zone, theresulting Projector Radiation Pattern will vary across the scan zone dueto dispersion of light as distance increases and due to structuraldifferences in the light as it proceeds from its source. FIG. 5A showsan example of varying amplitude (along relative Amplitude axis 51) ofProjector Radiation Pattern at positions along the graph's Y-axis (whichcorresponds to the scan zone's horizontal Y-axis in FIG. 2). The radianamplitude by a light sensor is low at position 55, rises rapidly toposition 54, continues rising past 55 although less steeply, peaks at56, and then descends rapidly past position 57. FIG. 5B showscorresponding lines of amplitude response for different heights of thegray card within the scan zone, that is, at different positions (X=24,X=28, and X=32) along the vertical X-axis of FIG. 2.

FIG. 6A shows a corresponding variation in Raw Image Intensity picked upby Camera 0 when an LED illuminator (32 in FIG. 2) projects light acrossseveral adjoined reflective gray cards in the scan zone (22 in FIG. 2).The resulting image pixels of line 67A start off low near Raw ImageIntensity axis 61, increasing until there is an aberrant and sudden dipat 63A (which corresponds to the geometric location of a small gapbetween gray cards in the scan zone), increases again to peak 66A andcurves downward slightly to the next aberrant and sudden dip at 64B(which corresponds to the geometric location of another small gapbetween gray cards in the scan zone), and proceeds downward to a thirdaberrant and sudden dip at 65A (which corresponds to a third small gapbetween adjacent gray cards in the scan zone.

FIG. 6B shows a comparable Raw Image Intensity line 67B that is pickedup by Camera 1, with again, aberrant dips at 63B, 64B, and 65B. Noticehowever that the positions of those dips (which likewise correspond tosmall gaps between adjacent gray cards in the scan zone) are atdifferent pixel numbers for Camera 1 than they were for Camera 0 in FIG.6A—this is a result of the different positions and perspectives ofCameras 0 and 1. Also note that although the peak intensity for Camera 0in FIG. 6A at 66A came before (to the left of) aberrant dip 64A, acomparable position (such as 66B) past pixel 400 on FIG. 6B has not yetreached the peak intensity seen by Camera 1, which peak occurs at apixel number (on y-axis 62) that is actually past aberrant dip 64B andpast pixel 600 on FIG. 6B. Each of Camera 0 and Camera 1 is recordingimage data from the same target object—but the image data is different.It still remains to somehow take the best of each set of image data foreventual use.

The results shown in FIGS. 6A and 6B are then used to obtain FlatteningCoefficients (e.g. for an illuminator Brightness of 220) for each ofCamera 0 and Camera 1, as shown in FIGS. 7A and 7B. In their bracketedsubtitle “For Brightness =220”, the “220” refers to the level on abrightness scale ranging from 1-256. In both FIGS. 7A and 7B, therequired Flattening Coefficient value starts off high at low PixelNumbers on axis 72, gradually diminishes past points 73A (FIG. 7A, forCamera 0) and 73B (FIG. 7B, for Camera 1), bottoming at 74A and 74Brespectively, and rising again past 75A and 75 B respectively.Interpolations are used in place of the aberrant dips from FIGS. 6A and6B respectively to obtain the Flattening Coefficients for the pixels ofeach of Cameras 1 and 2 across the scan zone.

In the “Flattening” method, a sample target of known, essentiallyuniform diffuse reflective properties is imaged at a known distance,while being illuminated by each respective illumination source andcamera to be used in the system. A “Nominal Flat” signal level isselected (considering minimum and maximum Raw signal amplitudes anddynamic range of downstream processing). Coefficients for each pixel inthe imaging system are determined, such that each pixel's coefficient,when multiplied by the amplitude of its corresponding Raw image pixelamplitude, will render a Nominal Flat pixel amplitude value (as near asquantization and other noise sources allow) linearly correlatable to theknown reflective properties of the target. Following flattening, imagesfrom both cameras are considered normalized on a reflectivity responsebasis.

Saving the Flattening Coefficients for all pixel numbers for each Camerareflected from the scan zone enables the processing of Raw Image Datafrom each Camera into Flattened Image Data from each Camera. FIG. 8shows the method and apparatus to be used: the illuminator 16 projectslight onto a uniform sample target 81, camera 1 records a nominal flatsignal 82 for a first Pixel at coordinates x and y in a plane in thescan zone and a Flattening Coefficient 83 is derived for that Pixel. Theprocess is repeated in a loop 84 until a table of FlatteningCoefficients is built up for all relevant pixel positions to get, forexample, a brightness level of 220 out of a maximal 256 for that camera.

FIG. 9 is a spreadsheet table for successive pixels assembled with RawData column 91 and Camera 1 GrayCard Flattening Coefficients column 92,taken at 24 inches between the scan head and the target. The tableproceeds with Target Flattened Column 93 and Ortho Target Column 94 thatreflect the Gridizing process, which turns Flattened Data for a pixelinto Ortho data for the same camera. A family of co-efficients thusderived (for example, every potentially applicable ¼ inch between thescan head and the target). The applicable Flattening Coefficient canthen be applied to each line of raw data such as shown in FIG. 6.

Once both the data from Camera 0 and the data from Camera 1 areprocessed into Ortho 0 and Ortho 1 data via the Gridizing process, therespective sets of data from Camera 0 (C0) and Camera 1 (C1) can thenand only then be compared on a pixel (C0,x,y) by pixel (C1,x,y) basis,where each corresponds to the same pixel-area on the target objectitself.

FIG. 10A illustrates the result of applying the Flattening coefficientsto Camera 0's Graycard Target Image data. For Pixel Numbers along axis102, the Flattened Intensity along axis 101 is slightly variable alongline 106A, with the exceptions of aberrant dips 103A, 104A, and 105A,which still represent the small gaps between adjacent gray cards.Likewise in FIG. 10B, the Flattened Graycard Target for Camera 1 isshown, with the aberrant dips 103B, 104B, and 105B along 106B alsorepresenting the same small gaps between adjacent gray cards in thetarget scan zone, but being at different pixel numbers for Camera 1 (inFIG. 10B) than the aberrant dips were for Camera 0 (in FIG. 10A). Theeffect of parallax can still be seen in the different locations of thecorresponding aberrant dips as between FIGS. 10A and 10B.

FIG. 11 shows the problem of parallax in attempting to compare pixeldata from one camera with pixel data from another camera, where theobjective is to obtain an enhanced image of the same area on a targetusing image data from both cameras. The surface line between points 112and 113 on a scan zone target object 118 can be seen by a camera at scanhead location 110 with pixels along line 114 on a nominal 1:1 basis.However, a second camera at scan head location 111 sees the same surfaceline between points 112 and 113 with a narrower set of pixels, alongline 115. The two perspectives' parallax is reversed for the surfaceline between points 116 and 117 on the target object 118. The effect isthat pixels from either camera are covering more territory on the targetwith each pixel farther out than a camera pixel covering an area on thetarget object directly below the camera. An orthographic perspective isone taken as if with a camera at an infinite distance away from thetarget.

FIG. 12A shows a graph of Flattened and Gridized Intensity axis 121 forGridized Pixels axis 122 for Camera 0's view of the Graycard. TheGridizing corrects for parallax for Camera 1 by moving its image datafrom FIG. 10A an increasing fraction of a pixel over as its parallaxincreases along the corresponding target surface. The Flattened andGridized Intensity line 125A data ceases relevance at 123A on the leftand 124A on the right. In between, the aberrant dips at 126A and 127Acan still be seen, reflecting the graycard small gaps. FIG. 12B showsthe corresponding Flattened and Gridized Intensity data for Camera 1. Itwill be noticed that the left and right irrelevance boundaries 123B and124B in FIG. 12B now align with the corresponding 123A on the left and124A on the right in FIG. 12B. Similarly, the aberrant dips 126B and127B in FIG. 12B now align with the corresponding dips 126A and 127A inFIG. 12A. The lines 125A and 126B are not identical. They are however,now meaningfully comparable on a pixel-by-pixel basis. Each value forintensity for a given Gridized Pixel Number on FIG. 12A (Camera 0) canbe compared to the corresponding Gridized Pixel Number on FIG. 12B(Camera 1), because each now represents the same location on the targetobject.

FIG. 13 shows a scan head 131, a board of lumber 132, a coded lightpattern 133 emitted by a laser. When the lumber 132 is passed through ascanning pattern of bars of coded light, the reflection back to a camerafrom the lumber will show information in the reflected light from whicha geometric shape of the lumber can be calculated. The geometric shapecan be mapped with coordinates. U.S. Pat. No. 5,615,003 (Electromagneticprofile scanner) and U.S. Pat. No. 5,986,745 (co-planar electromagneticprofile scanner) show in detail a system for determining the shape anddimensions of a surface of an object includes a projector for projectingonto the object a spatially coded pattern of radiation, for example,laser light. That system also includes a receiving device capable ofimaging the reflected pattern, and a discriminator for determining whichportion of the reflected pattern corresponds to which portion of theprojected pattern. By this means, a received signal representing lessthan the complete reflection from the projected pattern can becorrelated with a discrete portion of the scanned object. The procedureis repeated to obtain enough reliable data to generate a reasonablyreliable surface profile. The resulting set of received signals andcorrelations are used to calculate the shape and dimensions (geometricprofile) of the object.

The surface appearance of lumber and other objects gives usefulinformation, over and above its mere geometric profile, as to thelumber's characteristics. For example, knots are of paramount concern infinished lumber. Besides being either aesthetically desirable orundesirable for a particular application, wood knots present astructural problem, although they would not show well or at all in amere geometric profile of a board of lumber (except to the extent theknots corresponded exactly with ridges or depressions in the geometricprofile). Often a surface on a board of lumber is smooth enough thatknots, while present and visible, do not show well or at all in ageometric profile of the board. Knots are tougher to saw than un-knottedwood, yet define areas of weakness in lumber along which it is likely tocrack. It is generally preferable to have a knot embedded in a piece offinished lumber than to have it on a surface or an edge.

FIG. 14A shows a Raw Image Intensity axis 141, pixel Number axis 142, agraph of Raw Image data from Camera 0 of a striped target. A surfaceaberration 146A is apparent. Notice also the shape of the high intensitybars at 143A, 144A, and 145A. They correspond to the surface aberration146B, and the high intensity bars 143A, 144B, and 145B in FIG. 14B,although the those features are at different pixel numbers in FIGS. 14Aand 14B.

FIGS. 15A and 15B show the same data, but Flattened and Gridized forCamera 0 and Camera 1 respectively. Once past the irrelevance marker ofhigh intensity at 153A and 153B, the data is generally flat in responseat both the upper (highly lit and reflective) and lower (dark andnon-reflective) ends of the bars. The detailed shape of the bars at154A, 155A, 156A is somewhat similar to the corresponding features at154B, 155B, and 156B. The main point is that the vertical Flattened andGridized Intensity axis 151 data at those points can be compared betweenCamera 0 and Camera 1 because both sets of data are now aligned alongthe horizontal Gridized Pixel Number axis 152. The aberrationrepresented by Flattened and Gridized image data at 157A and 158B is ofparticular interest because the details of intensity vary so much inthat area depending on perspective. In such an area of interest, thedetermination of which pixel of intensity as between Camera 0 and Camera1 provides the most informative data for an enhanced image is bestillustrated by actual images of actual lumber.

FIG. 16A shows a Raw Image from Camera 0 of a board of lumber on whichthere is a first selected large knot 163A, an area of specularreflection 164A, a second selected large knot 165A, a first selectedsmall knot 166A, a second selected small knot 167A, an area 160A withoutspecular reflection, a third selected small knot 168A, and fourthselected small knot. FIG. 16B shows the same board of lumber passingthrough the scan zone but its Raw Image, taken at the same time, is fromCamera 1. Both FIGS. 16A and 16B are mapped onto a pixel number axis 162(corresponding to Y-axis 26 in FIG. 2) and scan number axis 161 (fromthe array of linear scans accumulated for each y-axis scan. In FIG. 16B,the image of the first selected large knot (163A in FIG. 16A) is labeled163B, and so on for the corresponding second selected large knot 165B,the first selected small knot 166B, the second selected small knot 167B,the third selected small knot 168B, and the fourth selected small knot169B. In FIG. 16B, the area of specular reflection at 160B is in acompletely different area on the same board than the specular reflectionat 164A in FIG. 16A. The different areas of specular reflection in theimages of the board of FIGS. 16A and 16B result in peculiarities ofbright image data that is problematic when attempting to compare imagepoint data over the entire board in order to read accurately actualsurface anomalies.

Referring to FIGS. 16A and 16B, both raw images are generated bycombining a successive number of linear scans of a section of a board.The linear scans from each camera were acquired simultaneously. Threekey distortions can be observed in these images:

-   -   1) Parallax—in the pixel dimension. A feature (knot 163A) is        observed in FIG. 16A at approximately scan number 125, and pixel        number 350, while the same feature (knot 163B) appears in FIG.        16B at the same scan number 125 but pixel number 300.    -   2) Specular Reflection of light source—In the Raw Image of        Camera 0, one can see brighter amplitudes from approx. pixels        350 to 600 due to the specular component of reflection from the        target. The same applies to the Raw Image acquired by Camera 1        from approx. pixels 550 to 800. Note, and this is key, specular        reflection will not originate from the same location on the        target in both images, due to geometric displacement of the        cameras with respect the illumination source. Specular        reflection is that light for which the light rays from the        illumination source have equal but opposite angles of incidence        and reflection from the target.    -   3) Variations due to the Radiation pattern of the illumination        source and responsiveness of the cameras along the pixel number        axis.

FIG. 17A shows the Flattened and Gridized (IE. Ortho) image from Camera0, derived by the method and apparatus of the present invention from theRaw Image Data illustrated with the same board in FIG. 16A. FIG. 17Bshows the Flattened and Gridized, IE. Ortho, image from Camera 1,derived by the method and apparatus of the present invention from theRaw Image Data illustrated with the same board in FIG. 16B. The pixelnumber 172 and the scan number axis 171 give coordinates for the lumberat the moment of imaging that are provided via the position encoder 18and computer control 19 of FIG. 1. Because these coordinates and bothimages have been Gridized to Ortho Images, the first selected large knotat 173A and 173B, the second selected large knot at 175A and 175B, thesecond selected small knot at 176A and 176B, the third selected smallknot at 178A and 178B, and the third selected small knot at 179A and179B can both be aligned visually and be compared by a computer on apixel-by-pixel coordinate basis. The areas of specular reflection 174Aand 177B (compare the corresponding areas without specular reflection174B and 177A) are obviously at quite separate areas on the same board.

FIG. 18 shows the method and apparatus of arriving at an Enhanced imagefrom Ortho Image data such as shown from Camera 0 and from Camera 1 inFIGS. 17A and 17B. An Orthographic Scan 0 provides camera 0 PixelIntensity data 182 at coordinates x and y (Pixel (OS0, x,y)). Likewisean Orthographic Scan 1 provides camera 0 Pixel Intensity data 183 atcoordinates x and y (Pixel (OS1, x,y)). The pixels are compared atcompare module 184, and a value from the pixels (for example, the leastintense value pixel, in a Minimum finder 185, would eliminate specularreflection from one camera in favor of a diffuse reflection intensityvalue from the other camera) is selected for assembly of the EnhancedImage 186. The Ortho Scan 0 data loop 187 and the Ortho Scan 1 data loop188 repeat the process for successive pixels, and so on.

FIG. 19A shows three intensity lines of data from a scan line across theboard shown in FIGS. 16A, 16B, 17A, 17B and 19B: a Camera 0 Ortho 0 dataline, which has areas of overly intense image data at, for example, 193Aand 194A, a Camera 1 Ortho 1 data line, which likewise has overlyintense image data in different pixel locations, for example at 195A and196A, and an Enhanced Image data line 194B which has been selected pixelby pixel from the other two lines by the method of FIG. 18, yielding,for example, point 193B from the Camera 1 Ortho 1 data line (rather thanthe data at 193A from Camera 0 Ortho 0) and point 195B from the Camera 0Ortho 0 data line (rather than the data at 195A from Camera 1 Ortho 1).Areas of high image data intensity such as 196B on the Enhanced Imagedata line reflect an actual anomaly, in this case an edge on the board.The area (approximately from pixel 930 to pixel 990) between thevertical line below 196A and the vertical line below 196B has only onedata line—only one camera provides data here due to parallax. Likewisethere is only a single data line (from the other camera) on the extremeleft in FIG. 19A up to about pixel 95. The scan window in which theinvention method is valid is where the data from both the first andsecond camera overlap, for example, pixel 128 to pixel 896 along pixelnumber axis 192. It is convenient to reduce the operable scan window toknown increments such as plus and minus 12 inches of target width from acenter line below the center of the scan head—this would be from pixel128 to 896 in FIG. 19B, along pixel number axis 192, In FIG. 19A, thevertical axis 191A is Flattened and Gridized Intensity. Thehorizontal-axis is Gridized pixel number across the scan line depictedfor the two Ortho data lines and the resultant Enhanced data line. Anarray of such Enhanced Image data lines can be assembled into completeEnhanced Images such as is shown in FIG. 19B.

FIG. 19B shows an actual Enhanced Image from the method and apparatus ofthe invention. The vertical scan number axis 191 and the horizontalpixel number axis 192 relate to the scan respective number axis andhorizontal axis in each of FIGS. 16A, 16B, 17A, and 17B, They do notcorrespond on a linear basis, however, because the parallax has beenremoved in the process from FIGS. 16A and 16B through to the EnhancedImage of FIG. 19B. That image is of the same actual board as was imageddifferently in FIGS. 16A, 16B, 17A, and 17B. In the Enhanced Image ofFIG. 19B, the specular reflection of the earlier images is eliminated.The selected features (large knots 193 and 195, and small knots 196,198, 199) are not only clear but are now accurately sized. The formerareas of specular reflection at 194 and 197 respectively have beeneliminated. Even the wood grain in both those areas can now beaccurately read by a machine. To summarize, the final Enhanced Image inFIG. 19B is void of specular reflections, is compensated for variationsin illumination radiation pattern and camera sensitivities, and itssurface features (knots, grain patterns) as represented aregeometrically correct with respect to the actual target object.

Referring to FIG. 20, it will be seen that multiple scan heads 210, 211,212, and 213 can be positioned over a long length of lumber consistingof board scan segments 214, 215, 216, and 217. The fields ofillumination and cameras' view 221, 222, 223, and 224 from therespective scan heads should overlap the board scan segments. This willenable multiplexing of the scan head so that overlapping scans can bedone by adjacent scan heads around the board scan segment lines 218,219, and 200. Preferred pixel values can then be selected for the linesbetween board scan segments, in the same manner as described above,rather than needlessly dealing with un-enhanced image data as stitchlines. The dotted lines between the board scan segments 214, 215, 216and 217 are shown for explanatory purposes but in practice thecorresponding stitch lines are rendered essentially invisible by theapplication of the Enhanced Imaging method and apparatus hereindisclosed.

The control and timing of sequential flashing of different illuminatorsto record the same target object locations on a pixel-by-pixel andline-by-line bases works well if the time between flashes is ofsufficiently short duration that the relevant sequential illuminationsare effectively simultaneous having respect to the timing and resolutionlimits of the equipment. For example, if 40 inches of target boardsurface pass under the scanner head every second, and 1000 scans persecond are taken with a coded laser alternating with 1000 scans persecond taken with an LED array and first and second color cameras,during a pair of alternate scans (½ a millisecond between scans) theboard has only traveled about 0.020 of an inch during the pair ofalternate scans, which is well within computational limits forcorrelating to pixel resolution—effectively the process works as well asif the scan were taken with the target not moving at each scan, and thenadvanced between scans and is analogous to moving events appearing to befrozen during strobe light illumination. Whether or not both monochromeand color illumination and camera apparatus are used, the Enhanced Imageof the present invention is made from combining data from single scansby two different cameras that have received light reflected by thetarget surface from at least one illuminator.

The enhanced, accurate imaging method of the present invention may beapplied with:

-   -   a) two or more cameras that are sensitized to the illuminator's        output and are viewing the same area on the target;    -   b) multiple special target illuminators and correspondingly        sensitized multiple cameras;    -   c) a multiplicity of area cameras and ambient lighting;        with multiple parallel stages (two of which are illustrated in        FIG. 1) for the image data from each camera accordingly used        before the Selective combining. Additional orthographic image        data from at least one additional camera (over Camera 0 and        Camera 1) can be compared with first camera orthographic image        data and second camera orthographic data for a coordinate        position on the target object, and a value of the orthographic        image data for a particular coordinate position on the target        object can be selected based on a pre-selected criteria for use        of first, second, and additional orthographic data in assembling        an enhanced image.

Additionally, the method and apparatus of the present invention can beapplied to the imaging of an object's internal interfaces (e.g. oflaminate material), when suitable penetrating radiation is reflectedfrom such internal interfaces and detectable (as reflected) by asuitable receiver.

The system may optionally provide Enhanced Images that are additionallyenhanced in detail by using different cameras having differentappropriate focal lengths or different wavelength sensitivities. Thesystem can yield improved results if successive Red, Green and Bluescans are taken quickly enough to be effectively simultaneous within thelimits of resolution of the equipment. The RGB scans can be compared,and Red, Green or Blue pixels can be discarded if they are unusual whencompared with the corresponding pixel of the other two colors. Smallimages errors due to vibrations and slight misalignment of the equipmentas the scanning proceeds can be eliminated by this method. Varyingexposure times as between the first and second cameras is also possiblewith this invention, because the pixels recorded by each camera areidentifiable and mappable on a one-to-one basis, that is, they can bematched in time and space, and compared, in order to select the moreinformative or more useful pixel data value. The invention enables thecomparing of different perspective images of a moving object on acorresponding pixel by pixel basis and coalescing a new image from thetwo sets of pixel data that draws on the more informative or more usefulpixels from each set.

In the Selective combining method described above, the lowest intensitypixel level was selected from each of the two Ortho Images to render anEnhanced Image absent of specular reflection. Just as both Ortho imagesare comparable with the present method and apparatus, both on a pixel bypixel basis and on a responsiveness basis, other image selectioncriterion may be applied to this method. Possible other selectioncriteria include, but are not limited to: pixel intensity, absence orpresence of specular reflection, specific color intensity level in amulti-color image, local variation in intensity, focus or any othercriteria which is deterministic within the sets of image data. Focus,for example, can be quantified based on the magnitude of firstdifferences, said first differences being in one or both dimensionswithin the image.

Higher dynamic range may be achieved by using the method and apparatusof the present invention and controlling the exposure time of one of thecameras with respect to the other camera. For example, if Camera 0 hasan exposure time of 10 mSec., and Camera 1 has an exposure time of 10/64mSec, the orthographic images can be combined to increase pixel depth inthe Enhanced image by a factor of 64 (6 bits).

Variants within the scope of the invention will be apparent to thoseskilled in the field of the invention. For example, the illuminationsource for the acquisition of the raw image data may be a laser, an LED,incandescent or any other light source or array of the same. Theinvention essentially provides a fast, versatile and effective way ofgenerating accurate enhanced images based on multiple camera image data,with selective combining of the best portions of that data enabled bythe apparatus set-up and the intermediate processing of the respectivecamera's image data with the steps disclosed above and as set out in theClaims hereto.

1. A method for generating accurate, high quality images comprising thesteps of: a) acquiring a first raw scan of a portion of a target objectacross a scan line in a scan zone with a first camera and simultaneouslyacquiring a second raw scan of the same portion of the target objectacross the scan line in the scan zone with a second camera, the secondcamera being separated from the first camera in a camera zone such thatthe first and second camera have substantially different perspectives ofthe same portion of the target object; b) converting the first raw scanfrom analog to digital format resulting in first raw image data andconverting the second raw scan from analog to digital format resultingin second raw image data; c) processing the first raw image data with afirst set of flattening coefficients derived from measurements ofvariations in illumination and in first camera response across the scanline to a uniform diffusely reflecting target in the scan zone,resulting in first flattened image data from the target object, andprocessing the second raw image data with a second set of flatteningcoefficients derived from measurements of variations in illumination andin second camera response across the scan line to the uniform diffuselyreflecting target in the scan zone, resulting in second flattened imagedata from the target object; d) compensating for parallax in firstflattened image data with a first set of calculations, resulting infirst orthographic image data,; and compensating for parallax in secondflattened image data with a second set of calculations, resulting insecond orthographic image data; e) comparing first orthographic imagedata corresponding to a coordinate location on the target object withsecond orthographic image data corresponding to the coordinate locationon the target object; f) selecting a pixel intensity value, for use asenhanced image data representing the coordinate location on the targetobject, from: i) the first orthographic image data corresponding to thecoordinate location ii) the second orthographic image data correspondingto the coordinate location; iii) a result of a formula using acombination of the first and second orthographic data corresponding tothe coordinate location.
 2. The method of claim 1, in which the steps ofclaim 1 are repeated with scanning of sequential scan lines across thetarget object, resulting in sequences of enhanced image datarepresenting corresponding coordinate locations on the target object,and assembling an enhanced image of the target object from the sequencesof enhanced image data.
 3. The method of claim 2, in which movement ofthe target object during scanning is controlled to maintain a knownimage aspect ratio during scanning and to avoid t distortion of theenhanced image.
 4. The method of claim 3, in which an electronic signalfrom a z-axis position encoder is used during the scanning to indicatetarget object position relative to a reference position for the scanzone.
 5. The method of claim 4, in which scans are triggered by theposition encoder at known incremental intervals of a target objectmovement through the scan zone.
 6. The method of claim 1, in which pixelintensity value selected for use as enhanced image data is a lower oftwo corresponding orthographic pixel data values from first orthographicdata and from second orthographic data, thereby selecting lower specularreflection from the target object.
 7. The method of claim 1, in whichgeometric positions of relevant portions of the target object areobtained by structured light geometric scanning, enabling mapping offirst raw data pixels to corresponding second raw data pixels.
 8. Themethod of claim 7, in which: an uncoded laser illuminator is used inconjunction with a monochrome camera to obtain at least one set ofmonochrome raw image data.
 9. The method of claim 7, in which an LEDilluminator is used in conjunction with a color camera to obtain atleast one set of raw image data.
 10. The method of claim 7, in whichalternate firing from a structured light geometric scanning illuminatorto obtain target object position data, and from a raw image datailluminator is effectively simultaneous with respect to scanningmovement of the target object by having a time between flashes from therespective illuminators sufficiently short that a computed adjustment ofcoordinate positions to compensate for scanning movement of the targetobject between firings is within computational limits for correlatingresulting structured light geometric scanning data and corresponding rawimage data to pixel resolution.
 11. The method of claim 1, in which twodimensional enhanced images are generated by combining a successivenumber of linear scans of a surface.
 12. The method of claim 1, inwhich: a) processing of the first raw image data with a first set offlattening coefficients derived from measurements of variations inillumination and in first camera response across the scan line to auniform diffusely reflecting target in the scan zone, resulting in firstflattened image data from the target object, and b) processing thesecond raw image data with a second set of flattening coefficientsderived from measurements of variations in illumination and in secondcamera response across the scan line to the uniform diffusely reflectingtarget in the scan zone, resulting in second flattened image data fromthe target object, are performed to a standard level of image flatteningwith multiple identical adjacent scan heads each using an illuminator, afirst camera and a second camera, and the processing method of claim 1;and multiple flattened images of adjacent areas on the target belowadjacent scan heads obtained by such processing are joined to form anoverall image of the target without discontinuity of image accuracybetween multiple flattened images from respective adjacent scan heads.13. The method of claim 1, in which multiple images of adjacent areas onthe target object are joined together along a geometrically exact pixelstitch line, in order to minimize discontinuity of target objectfeatures and discontinuity of image intensity values for adjacentgeometric locations on the target object to below image background noisevalues.
 14. The method of claim 1, in which a geometric profile of thetarget is derived using a structured light geometric scanner, and an LEDis used to illuminate the target object for the first and second camerasduring an image capture scan.
 15. The method of claim 1, in whichadditional orthographic image data from at least one additional camerais compared with first camera orthographic image data and second cameraorthographic data for a coordinate position on the target object, and avalue of the orthographic image data for a particular coordinateposition on the target object is selected based on a pre-selectedcriteria for use of first, second, and additional orthographic data inassembling an enhanced image.
 16. The method of claim 2, in which: a)movement of the target object during scanning is controlled and measuredmaintain a known image aspect ratio during scanning and to avoiddistortion of the enhanced image; b) an electronic signal from a z-axisposition encoder is used during the scanning to indicate target objectposition relative to a reference position for the scan zone; c) scansare triggered by the position encoder at known incremental intervals ofa target object movement through the scan zone; d) pixel intensity valueselected for use as enhanced image data is a lower of two correspondingorthographic pixel data values from first orthographic data and fromsecond orthographic data, thereby selecting lower specular reflectionfrom the target object.
 17. The method of claim 2, in which: a)geometric positions of relevant portions of the target object areobtained by structured light geometric scanning, enabling mapping offirst raw data pixels to corresponding second raw data pixels; b)alternate firing from a structured light geometric scanning illuminatorto obtain target object position data, and from a raw image datailluminator is effectively simultaneous with respect to scanningmovement of the target object by having a time between flashes from therespective illuminators sufficiently short that a computed adjustment ofcoordinate positions to compensate for scanning movement of the targetobject between firings is within computational limits for correlatingresulting structured light geometric scanning data and corresponding rawimage data to pixel resolution.
 18. The method of claim 2, 16, or 17, inwhich two dimensional enhanced images are generated by combining asuccessive number of linear scans of a surface.
 19. The method of claim2, 16, or 17, in which: i) processing of the first raw image data with afirst set of flattening coefficients derived from measurements ofvariations in illumination and in first camera response across the scanline to a uniform diffusely reflecting target in the scan zone,resulting in first flattened image data from the target object, and ii)processing the second raw image data with a second set of flatteningcoefficients derived from measurements of variations in illumination andin second camera response across the scan line to the uniform diffuselyreflecting target in the scan zone, resulting in second flattened imagedata from the target object, are performed to a standard level of imageflattening with multiple identical adjacent scan heads each using anilluminator, a first camera and a second camera, and the processingmethod of claim 1; and b) multiple flattened images of adjacent areas onthe target below adjacent scan heads obtained by such processing arejoined to form an overall image of the target, in which multiple imagesof adjacent areas on the target object are joined together along ageometrically exact pixel stitch line, in order to minimizediscontinuity of target object features and discontinuity of imageintensity values for adjacent geometric locations on the target objectto below image background noise values.
 20. The method of claim 2, 16,or 17 in which a geometric profile of the target is derived using codedlight from a laser, and an LED is used to illuminate the target objectfor the first and second cameras during an image capture scan. 21.Apparatus for generating accurate, high quality images comprising: a) atleast two cameras, including a first camera set up for acquiring a firstraw scan of a portion of a target object across a scan line in a scanzone with a first camera and simultaneously acquiring a second raw scanof the same portion of the target object across the scan line in thescan zone with a second camera, the second camera being separated fromthe first camera in a camera zone such that the first and second camerahave substantially different perspectives of the same portion of thetarget object; b) an analog to digital converter set up for convertingthe first raw scan from analog to digital format resulting in first rawimage data and converting the second raw scan from analog to digitalformat resulting in second raw image data; c) a flattening imageprocessing module that processes the first raw image data with a firstset of flattening coefficients derived from measurements of variationsin illumination and in first camera response across the scan line to auniform diffusely reflecting target in the scan zone, resulting in firstflattened image data from the target object, and that processes thesecond raw image data with a second set of flattening coefficientsderived from measurements of variations in illumination and in secondcamera response across the scan line to the uniform diffusely reflectingtarget in the scan zone, resulting in second flattened image data fromthe target object; d) a gridizing image processing module thatcompensates for parallax in first flattened image data with a first setof calculations, resulting in first orthographic image data, andcompensates for parallax in second flattened image data with a secondset of calculations, resulting in second orthographic image data; e) aselective combining image processing module that compares firstorthographic image data corresponding to a coordinate location on thetarget object with second orthographic image data corresponding to thecoordinate location on the target object and selects a pixel intensityvalue, for use as enhanced image data representing the coordinatelocation on the target object, from: i) the first orthographic imagedata corresponding to the coordinate location; ii) the secondorthographic image data corresponding to the coordinate location; iii) aresult of a formula using a combination of the first and secondorthographic data corresponding to the coordinate location.
 22. Theapparatus of claim 21, further comprising a computer set up to obtainsequential scan lines across the target object and sequences of enhancedimage data representing corresponding coordinate locations on the targetobject, and to assemble an enhanced image of the target object from thesequences of enhanced image data.
 23. The apparatus of claim 21, furthercomprising a position encoder set up to track movement of the targetobject during scanning in order to maintain a known image aspect ratioduring scanning and to avoid distortion of the enhanced image
 24. Theapparatus of claim 23, in which the position encoder outputs anelectronic signal during scanning to indicate target object positionalong a z-axis relative to a reference position for the scan zone. 25.The apparatus of claim 23, in which the position encoder triggers scansat known incremental intervals of a target object movement through thescan zone.
 26. The apparatus of claim 21, in which the selectivecombining image processing module selects for use as enhanced image dataa lower of two corresponding orthographic pixel data values from firstorthographic data and from second orthographic data, thereby selectinglower specular reflection from the target object.
 27. The apparatus ofclaim 21, further comprising a structured light geometric scanner forobtaining geometric positions of relevant portions of the target object,to enabling mapping of first raw data pixels to corresponding second rawdata pixels.
 28. The apparatus of claim 21, in which an uncoded laserilluminator is used in conjunction with a monochrome camera to obtain atleast one set of monochrome raw image data.
 29. The apparatus of claim21, in which in which an LED illuminator is used in conjunction with acolor camera to obtain at least one set of raw image data.
 30. Theapparatus of claim 21, in which a structured light geometric scanner toobtain target object position data, is set up to fire alternately buteffectively simultaneously with a raw image data illuminator withrespect to scanning movement of the target object, by being set up tohave a time between flashes from the respective illuminatorssufficiently short that a computed adjustment of coordinate positions tocompensate for scanning movement of the target object between firings iswithin computational limits for correlating resulting coded lasergeometric data and corresponding raw image data to pixel resolution. 31.The apparatus of claim 21, further comprising a computer that generatestwo dimensional enhanced images by combining a successive number oflinear scans of a surface;
 32. The apparatus of claim 21, furthercomprising a computer that: a) processes the first raw image data with afirst set of flattening coefficients derived from measurements ofvariations in illumination and in first camera response across the scanline to a uniform diffusely reflecting target in the scan zone,resulting in first flattened image data from the target object, and b)processes the second raw image data with a second set of flatteningcoefficients derived from measurements of variations in illumination andin second camera response across the scan line to the uniform diffuselyreflecting target in the scan zone, resulting in second flattened imagedata from the target object; to a standard level of image flattening,and coordinates multiple identical adjacent scan heads each using theapparatus of claim 21, and resulting multiple flattened images ofadjacent areas on the target below adjacent scan heads obtained by suchprocessing, to form an overall image of the target without discontinuityof image accuracy between multiple flattened images from respectiveadjacent scan heads.
 33. The apparatus of claim 21, in which a computerjoins multiple images of adjacent areas on the target object along apixel stitch line, to render discontinuity of target object features anddiscontinuity of image intensity values for adjacent geometric locationson the target object below background noise values.
 34. The apparatus ofclaim 21, in which a structured light geometric scanner obtains ageometric profile of the target object, and an LED illuminator is usedto illuminate the target object for the first and second cameras duringan image capture scan.
 35. The apparatus of claim 21, in which acomputer is set up to compare additional orthographic image data from atleast one additional camera with first camera orthographic image dataand second camera orthographic data for a coordinate position on thetarget object, and the computer selects a value of the orthographicimage data for a particular coordinate position on the target objectbased on a pre-selected criteria for use of first, second, andadditional orthographic data in assembling an enhanced image.
 36. Theapparatus of claim 22, further comprising a position encoder set up totrack movement of the target object during scanning in order to maintaina known image aspect ratio during scanning and to avoid distortion ofthe enhanced image, in which the position encoder outputs an electronicsignal during scanning to indicate target object position along a z-axisrelative to a reference position for the scan zone, and the positionencoder triggers scans at known incremental intervals of a target objectmovement through the scan zone.
 37. The apparatus of claim 21, furthercomprising: a) a structured light geometric scanner illuminator forobtaining geometric positions of relevant portions of the target object,to enabling mapping of first raw data pixels to corresponding second rawdata pixels; b) the structured light geometric scanner illuminator isset up to fire alternately but effectively simultaneously with a rawimage data illuminator with respect to scanning movement of the targetobject, by being set up to have a time between flashes from therespective illuminators sufficiently short that a computed adjustment ofcoordinate positions to compensate for scanning movement of the targetobject between firings is within computational limits for correlatingresulting geometric data and corresponding raw image data to pixelresolution.
 38. The apparatus of claim 22, 36, or 37, further comprisinga computer that generates two dimensional enhanced images by combining asuccessive number of linear scans of a surface;
 39. The apparatus ofclaim 22, 36, or 37 as part of an aligned multiplicity of suchapparatus, further comprising a computer that: a) processes the firstraw image data with a first set of flattening coefficients derived frommeasurements of variations in illumination and in first camera responseacross the scan line to a uniform diffusely reflecting target in thescan zone, resulting in first flattened image data from the targetobject, and b) processes the second raw image data with a second set offlattening coefficients derived from measurements of variations inillumination and in second camera response across the scan line to theuniform diffusely reflecting target in the scan zone, resulting insecond flattened image data from the target object; to a standard levelof image flattening, and coordinates multiple identical adjacent scanheads each using the apparatus of claim 21, and resulting multipleflattened images of adjacent areas on the target below adjacent scanheads obtained by such processing, to form an overall image of thetarget without discontinuity of image accuracy between multipleflattened images from respective adjacent scan heads; and joins multipleimages of adjacent areas on the target object along a geometricallyexact pixel stitch line, to render discontinuity of target objectfeatures and discontinuity of image intensity values for adjacentgeometric locations on the target object below background noise values.40. The apparatus of claim 22, 36 or 37, in which a laser provides codedlight to obtain a geometric profile of the target object, and an LEDilluminator is used to illuminate the target object for the first andsecond cameras during an image capture scan.